Method for making valve device

ABSTRACT

An opening degree sensor produces a sensor output corresponding to a valve opening degree of a valve, and includes a memory into which the sensor output corresponding to the valve opening degree is written. When performing a first half process, flow rates of more than one valve device are measured, a flow rate error is calculated based on an average flow rate obtained by averaging the measured flow rates, and the sensor output corresponding to the valve opening degree into which the flow rate error is incorporated is obtained. When performing a second half process, the sensor output corresponding to the valve opening degree obtained in the first half process is written into the memory of the valve device whose flow rate is not measured.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2015-48880filed on Mar. 11, 2015, the disclosure of which is incorporated hereinby reference.

TECHNICAL FIELD

The present disclosure relates to a method for making a valve devicethat controls a flow rate, and particularly to an art of writing asensor output corresponding to a valve opening degree.

BACKGROUND

As a specific example for a valve device that controls a flow rate, aconventional technology will be described using an exhaust gasrecirculation (EGR) valve (see, e.g., JP2009-002325A). The EGR valvethat operates a valve by an actuator includes an opening degree sensor(e.g., angle sensor) as a means for detecting an operation condition(valve opening degree) of the valve by the actuator.

An opening degree sensor provided for the EGR valve is set to produce a“predetermined sensor output” at the time of “a predetermined valveopening degree”. To describe an example for assisting the understanding,writing to a memory is carried out to produce the sensor output of 1.2 Vwhen the valve opening degree is fully closed, and the sensor output of4.0 V when the valve opening degree is fully open, in a productionprocess of the EGR valve. Accordingly, the mechanical “valve openingdegree” of the EGR valve and the electrical “sensor output” outputted bythe opening degree sensor correspond to each other.

Issues of the conventional technology will be discussed. There is arequest to “temporarily” open-control the EGR valve for flow rateadjustment. In recent years, there is a request to “constantly”open-control the EGR valve for flow rate adjustment. In this case (atthe time of open-control), the flow rate adjustment is made based on thesensor output from the opening degree sensor, so that a “flow rateobtained from the sensor output (referred to as an operation flow rate)”and an “actual flow rate through the EGR valve (referred to as an actualflow rate)” may correspond to each other.

However, despite the correspondence between the “valve opening degree”and the “sensor output”, a flow rate error (deviation of the increaseand decrease of the flow rate common to the EGR valves) may be causeddue to, for example, the variation (production error) in shape of acomponent that constitutes the EGR valve. As a result, the “operationflow rate obtained from the sensor output” and the “actual flow ratethrough the EGR valve” may not correspond to each other. Thus, eventhough the EGR valve produced by the conventional technology isopen-controlled, the flow rate of EGR gas cannot be controlled with highprecision.

Although the “issues of the conventional technology” have been describedabove using the EGR valve, they are not the issues caused only for theEGR valve. Another valve device, such as a valve disposed in a throttlevalve or turbocharger, also causes similar issues at the time ofopen-control.

SUMMARY

The present disclosure addresses at least one of the above issues. Thus,it is an objective of the present disclosure to provide a method formaking a valve device that can suppress increase in number of processesand make correspondence between an “operation flow rate obtained from asensor output” and an “actual flow rate through the valve device”.

To achieve the objective of the present disclosure, there is provided amethod for making a valve device including: a passage, a valve, and anopening degree sensor. Fluid passes through the passage. The valve makesopening degree adjustment of the passage. The opening degree sensorproduces a sensor output corresponding to a valve opening degree of thevalve, and includes a memory into which the sensor output correspondingto the valve opening degree is written. According to the method, a firsthalf process is performed, and a second half process is also performed.The valve device is one of more than one valve device. At the time ofperforming the first half process, flow rates of the more than one valvedevice are measured, a flow rate error is calculated based on an averageflow rate obtained by averaging the measured flow rates, and the sensoroutput corresponding to the valve opening degree into which the flowrate error is incorporated is obtained. At the time of performing thesecond half process, the sensor output corresponding to the valveopening degree obtained in the first half process is written into thememory of the valve device whose flow rate is not measured.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a sectional view illustrating an EGR valve in accordance witha first embodiment;

FIG. 2A is a flowchart showing a production process which illustrates aspecific example of a first half process in the first embodiment;

FIG. 2B is a flowchart showing the production process which illustratesa specific example of a second half process in the first embodiment;

FIG. 3 is a graph illustrating a relationship between a valve openingdegree and a flow rate in the first embodiment;

FIG. 4 is a graph illustrating a relationship between a nominal openingdegree and an actual opening degree in the first embodiment; and

FIG. 5 is a flowchart illustrating a production process in accordancewith a second embodiment.

DETAILED DESCRIPTION

Embodiments will be described.

A specific example (embodiment) of application of the present disclosureto an “EGR valve of an exhaust gas recirculation device (EGR device)”will be explained below. The embodiment discloses a specific example,and it goes without saying that the present disclosure is not limited tothe embodiment.

First Embodiment

A first embodiment will be described in reference to FIGS. 1 to 4. TheEGR valve adjusts an opening degree of an EGR passage 1 for returning apart of exhaust gas discharged by an engine (internal-combustion engine)to an intake passage of the engine as EGR gas. This EGR valve iscontrolled by an (engine control unit) ECU.

The EGR valve may be used for a high-pressure EGR system that returnsEGR gas from a high exhaust pressure generating range (upstream of aturbocharger) in an exhaust passage to the intake passage, or may beused for a low-pressure EGR system that returns EGR gas from a lowexhaust pressure generating range (downstream side of a catalyst orparticulate filter in an exhaust gas flow direction) in the exhaustpassage to the intake passage. As an example, FIG. 1 illustrates an EGRvalve used for the low-pressure EGR system.

The EGR valve includes a housing 2 that defines therein a part of theEGR passage 1, a valve 3 that is disposed in the EGR passage 1, a shaft4 that supports this valve 3, and an electric actuator 5 that givesrotation force to this shaft 4.

The electric actuator 5 includes an electric motor 6 that generates therotation force upon energization thereof, a deceleration device 7 thatamplifies a rotation output of this electric motor 6 to drive the shaft4, a return spring 8 that returns the shaft 4 (valve 3) to its initialposition (fully closed position), and an opening degree sensor 9 thatdetects an opening degree of the valve 3.

The above-described components will be explained below. The housing 2 ismade of a metallic material or a resin material excellent in heatresistance. An inner wall (bore) of the EGR passage 1 having acylindrical shape is formed in this housing 2, and a bolt inserting holefor fixing the EGR valve to a vehicle is provided at a bore end.

The housing 2 includes a shaft inserting hole through which the shaft 4is inserted and disposed. The shaft 4 passes across the EGR passage 1 ina right and left direction in FIG. 1, and is attached to the housing 2in a direction perpendicular to a streamline direction (bore axis) ofthe EGR passage 1. A bearing 11 that rotatably supports the shaft 4 isdisposed in the part of the shaft inserting hole through which the endof the shaft 4 (right side in FIG. 1) is inserted and disposed. Asealing plug 12 for sealing the end of the shaft inserting hole is fixedto the end of the shaft inserting hole (right end in FIG. 1).

Similarly, a bearing 13 (rolling bearing as an example) that rotatablysupports the shaft 4 is also disposed in the part of the shaft insertinghole through which a root side of the shaft 4 (left side in FIG. 1) isinserted and disposed. A seal material 14 for sealing a clearancebetween the housing 2 and the shaft 4 is disposed in the shaft insertinghole between this bearing 13 and the EGR passage 1.

The shaft 4 is a cylindrical rod that is formed from a metallic material(e.g., iron, stainless steel), and is supported rotatably by the housing2 as described above. On the other hand, the valve 3 is a butterfly-typerotation valve that is formed in a generally disk shape from a metallicmaterial (e.g., aluminum, brass), and is fixed to the shaft 4 in the EGRpassage 1. The art of joining of the valve 3 and the shaft 4 is notlimited, and the valve 3 and the shaft 4 are joined together, forexample, by a welding technique, or screw-fastening technique orcrimping technique. Although a seal ring-less type that does not use aseparate seal ring at an outer peripheral edge of the valve 3 isdisclosed in FIG. 1, this is, needless to say, not limiting.

The electric actuator 5 is attached to the above-described housing 2,and a gear cover 21, which can be attached and removed by a screw or thelike, is attached to the housing 2. The electric motor 6 is accommodatedin a motor accommodating chamber that is formed in the housing 2. Thedeceleration device 7, the return spring 8, and so forth areaccommodated in a space formed between the housing 2 and the gear cover21.

The electric motor 6 is a widely-known direct current motor that has itsrotation direction switched by the switch of the energizing directionand that generates rotation torque in accordance with the energizingamount. The electric motor 6 is inserted into the motor accommodatingchamber, and is then fixed to the housing 2 by a screw or the like.

The deceleration device 7 is a gear-type speed reducer that deceleratesthe rotation generated by the electric motor 6 through combination ofgears and that increases driving torque to transmit the torque to theshaft 4. The deceleration device 7 includes a motor gear (pinion gear)22 that rotates integrally with the electric motor 6, an intermediategear 23 that is rotated by this motor gear 22, and a final gear (gearrotor) 24 that is rotated by this intermediate gear 23. The final gear24 rotates integrally with the shaft 4.

The motor gear 22 is an external gear having a small diameter that isfixed to an output shaft of the electric motor 6. The intermediate gear23 is a double gear including a large-diameter gear 23 a and asmall-diameter gear 23 b which are provided concentrically with eachother. The intermediate gear 23 is supported rotatably by a supportingshaft 25 which is supported by the housing 2 and the gear cover 21. Thelarge-diameter gear 23 a is constantly engaged with the motor gear 22,and the small-diameter gear 23 b is constantly engaged with the finalgear 24. The final gear 24 is an external gear having a large diameterthat is fixed to the end portion of the shaft 4, and its engaging teeth(external teeth) are provided only in a range that is in accordance withthe rotation of the valve 3.

When an electric current supplied to the electric motor 6 isinterrupted, the return spring 8 returns the opening degree of the valve3 to its fully closed position. A specific example of the return spring8 is a single coil spring that is wound only in one direction, and isdisposed around the shaft 4 concentrically with the shaft 4 asillustrated in FIG. 1.

The opening degree sensor 9 of this embodiment is an angle sensor thatdetects a rotation angle of the shaft 4 to detect the opening degree ofthe valve 3, and gives a sensor output (voltage output) in accordancewith the rotation angle detected by the opening degree sensor 9 to theECU.

This opening degree sensor 9 is a magnetic-type rotation opening degreesensor 9 that contactlessly detects a relative rotation between twomembers. The opening degree sensor 9 is configured to include a magneticflux generating means 31 having a generally cylindrical shape that isinserted in the final gear 24 to rotate integrally with the shaft 4, amagnetic detection core 32 that is attached to the gear cover 21 toconverge the magnetic flux given from the magnetic flux generating means31 on its generally central part, and a Hall IC (memory) 33 that isattached to the magnetic detection core 32 to generate a sensor outputin accordance with the density of magnetic flux passing through thegenerally central part of the magnetic detection core 32.

The Hall IC 33 includes a Hall element that outputs a detection signalin accordance with the density of the passing magnetic flux (i.e.,signal in accordance with a rotation angle of the magnetic fluxgenerating means 31), a memory (e.g., rewritable ROM such as an EEPROM)into which a “sensor output corresponding to the detected openingdegree” is written, and an amplifying circuit that generates the outputsignal from the Hall element as the sensor output (voltage output)according to the valve opening degree based on the data written in thememory. The above configuration is obviously a specific example, and thememory and the amplifying circuit may be provided separately from theHall IC 33.

The background art for the first embodiment will be described below. TheECU is a widely known electronic control unit including a microcomputer,and open-controls the EGR valve “constantly” or “temporarily” to controlthe amount of EGR gas returned to the engine. In this case (at the timeof open-control), the ECU controls the EGR gas amount based on thesensor output outputted from the opening degree sensor 9.

To highly accurately control the EGR gas amount at the time ofopen-control, an “operation flow rate obtained from the sensor output”that is obtained from the sensor output, and an “actual flow rate” ofgas that actually flows through the EGR valve may correspond to eachother. However, an “error in flow rate” may be caused due to, forexample, the shape of the component that constitutes the EGR valve.Accordingly, the “operation flow rate obtained from the sensor output”and the “actual flow rate” do not correspond to each other, so that theflow rate of EGR gas cannot be controlled with high precision by theopen-control.

In this first embodiment, using occurrence of a “flow rate error” commonto more than one EGR valve produced, correspondence is made between the“operation flow rate obtained from the sensor output” and the “actualflow rate” of gas actually flowing through the EGR valve.

The method for making the EGR valve will be described below. Asdescribed above, the EGR valve (which is an example of a valve device)of this first embodiment includes the valve 3 that adjusts an openingdegree of the EGR passage 1 (which is an example of a passage), and theopening degree sensor 9 that produces the sensor output corresponding tothe opening degree of this valve 3. The opening degree sensor 9 includesthe memory into which the “sensor output corresponding to the valveopening degree” is written.

In a production process of the EGR valve, there are executed (a) a firsthalf process, where: the flow rates of more than one EGR valve aremeasured; the flow rate error is calculated based on an average flowrate obtained by averaging the measured flow rates; and the “sensoroutput corresponding to the valve opening degree (written-in data aftercorrection)”, in which this flow rate error is incorporated, isobtained, and (b) a second half process, where: the “written-in dataafter correction” obtained in the first half process is written into thememory of the EGR valve in which data is not written into the memory andwhose flow rate is not measured (i.e., EGR valve in which data issubsequently written into the memory).

In the specific first half process, there are executed (a1) an averageflow rate calculation process where flow rate measurement is carried outwith more than one EGR valve in which the “sensor output correspondingto the valve opening degree” is written into their each memory, tocalculate the “average flow rate (i.e., averaged actual flow rate”, and(a2) a matching process where three pieces of information: the averageflow rate, the sensor output, and the valve opening degree are matchedtogether.

In the specific matching process, the “sensor output corresponding tothe valve opening degree” that can make correspondence between the“operation flow rate obtained from the sensor output” and the “actualflow rate” is obtained using a relationship (see FIG. 3) between the“flow rate and valve opening degree” without errors and the “flow rateerror” obtained through measurement, or a relationship between the “flowrate and sensor output” without errors and the “flow rate error”obtained through measurement.

The specific example of the first half process will be described below.As described above, the first half process is a process in which: theflow rates of more than one EGR valve are measured; the “average flowrate error of the EGR valves” is recognized in advance based on theaverage flow rate; the three pieces of information of the “average flowrate”, the “sensor output”, and the “valve opening degree” are matchedtogether; and the “sensor output corresponding to the valve openingdegree” which is a “sensor output corresponding to the flow rate” isobtained.

The specific example of the first half process will be explained withreference to FIG. 2A. In the specific example illustrated below, the“valve opening degree is a valve angle” and the “sensor output is asensor voltage”. Step S1: the “sensor output corresponding to the valveopening degree” is written into the memory. As an example, data (e.g.,six-dimensional polynomial) with 1.2 V at the time of the valve anglebeing 0 degrees (valve opening degree is fully closed: 0% of the openingdegree), and with 4.0 V at the time of the valve angle being 70 degrees(valve opening degree is fully open: 100% of the opening degree) iswritten into the memory.

Step S2: the flow rate is measured using the EGR valve in which the datais written into its memory at the above Step S1 to obtain the actualflow rate for the sensor output. As an example, an actual flow rate Qaat the time of the sensor output being 4.0 V (fully open) is measured.

Step S3: the above Steps S1, S2 are repeatedly performed using more thanone EGR valve to calculate the average flow rate obtained by averagingthe actual flow rates. The average flow rate of the actual flow ratesfor the valve opening degree is indicated by a continuous line A in FIG.3. As an example, the average flow rate Qa-ave of the actual flow ratesQa is calculated. Although the number of EGR valves with which toperform the flow rate measurement is not limiting, using the more EGRvalves may be more desirable in terms of accuracy.

Step S4: a comparison is made between the “average flow rate of theactual flow rates for the valve opening degrees (see the continuous lineA in FIG. 3)” and a “design flow rate without an error for the valveopening degree (see a continuous line B in FIG. 3)”, and a correctionopening degree is calculated based on a flow rate difference (flow rateerror) therebetween. Specifically, when the EGR valve does not have aflow rate error, a difference is not made between a nominal openingdegree (design opening degree of the EGR valve) and an actual openingdegree (actual opening degree of the EGR valve) as indicated by a shortdashes line C in FIG. 4. On the other hand, when the EGR valve has aflow rate error, an error is caused in the actual opening degree (actualopening degree of the EGR valve) relative to the nominal opening degreeas indicated by a continuous line D in FIG. 4. Accordingly, thecorrection opening degree obtained by correcting the flow rate error isfound based on a difference between the nominal opening degree and theactual opening degree (nominal opening degree−actual opening degree). Asan example, a correction angle Da at 70 degrees of the valve angle(valve opening degree is fully open) is obtained.

Step S5: the correction opening degree obtained at the above Step S4 isincorporated into the valve opening degree. Then, the “sensor outputcorresponding to the valve opening degree” into which the correctionopening degree is incorporated (written-in data after correction by apolynomial or the like) is obtained. As an example, the “written-in dataafter correction” with 1.2 V at the time of the valve angle being 0degrees (valve opening degree is fully closed: 0% of the openingdegree), and with 4.0 V at the time of “valve angle 70°−correction angleDa” is obtained. This completes the first half process.

A specific example of the second half process will be described withreference to FIG. 2B. Step S11: the “sensor output corresponding to thevalve opening degree (written-in data after correction)” obtained in thefirst half process is written into the memory. This single processcompletes the second half process.

A first effect of the first embodiment will be described below.According to the method for making the EGR valve of this firstembodiment, the flow rate error is calculated from more than onepreviously-produced EGR valve, and the “sensor output corresponding tothe valve opening degree (written-in data after correction)” into whichthis flow rate error is incorporated is obtained (first half process).The “written-in data after correction” obtained in the first halfprocess is written into a memory of another subsequently-produced EGRvalve (second half process). Thus, the number of production processes ofthe EGR valve can be reduced.

According to the method for making the EGR valve of this firstembodiment, the “written-in data after correction” is obtained using theaverage flow rate of more than one EGR valve. As a result, influence ofa differential pressure variation caused during each individual flowrate measurement can be restrained. Thus, a defect such as variation in“written-in data after correction” due to the influence of thedifferential pressure variation caused during flow rate measurement canbe avoided, and highly accurate correspondence can thereby be madebetween the “operation flow rate” and the “actual flow rate”.

As described above, the method for making the EGR valve of this firstembodiment can make correspondence between the “operation flow rateobtained from the sensor output” and the “actual flow rate of EGR gasflowing through the EGR valve”, with the number of production processesreduced. Accordingly, even when open-controlling the EGR valve, the“operation flow rate” and the “actual flow rate” correspond to eachother. Thus, the flow rate of EGR gas can be controlled with highprecision. In addition, the reduction in number of production processescan suppress the cost of the EGR valve, to which a flow rate correctionis made.

A second effect of the first embodiment will be described below. In thefirst half process of this first embodiment, the flow rate measurementis carried out at more than one valve opening degree, i.e., the flowrate measurement is performed at two or more valve opening degrees. Inthis manner, making the flow rate measurement at more than one valveopening degree can improve the measurement accuracy of the “flow rateerror”. Thus, correspondence can be made between the “operation flowrate” and the “actual flow rate” in a wide opening degree range.

Specifically, the flow rate measurement is made with at least two valveopening degrees of the fully closed position and fully open positionincluded. In this manner, making the flow rate measurement at two ormore opening degrees including the fully closed position and fully openposition can make correspondence between the “operation flow rate” andthe “actual flow rate” in a wide opening degree range from a low openingdegree to a high opening degree. Additionally, in the case of flow ratemeasurement at each of many valve opening degrees, i.e., in the case offlow rate measurement at opening degrees of many positions, themeasuring point increases in number. Thus, the precision ofcorrespondence between the “operation flow rate” and the “actual flowrate” can be improved.

Second Embodiment

A second embodiment will be described with reference to FIG. 5. In thefollowing embodiments, the same numerals as in the above firstembodiment indicate their corresponding functional objects. In the abovefirst embodiment, the “first half process” and the “second half process”have been explained independently for the purpose of facilitatingunderstanding. On the other hand, this second embodiment repeatsreflecting the flow rate of the EGR valve that has completed the “secondhalf process” in the “first half process” for the subsequent EGR valve.

Specifically, in this second embodiment, the flow rate of the EGR valvethat has completed writing the data into the memory in the “second halfprocess” is measured, and the flow rate obtained by this flow ratemeasurement is reflected in the “sensor output corresponding to thevalve opening degree” used for writing the data into the memory for asubsequent EGR valve device. More specifically, each time themeasurement of the flow rate of the EGR valve that has completed writingthe data into the memory (flow rate inspection for the productinspection in this embodiment) is carried out, the second embodimentincreases the number of samples for calculating the average flow rate(i.e., number of samples for the flow rates used when calculating theaverage flow rate).

A specific example will be described with reference to FIG. 5. Step S11:as explained in the above first embodiment, the second half process isexecuted to write the “sensor output corresponding to the valve openingdegree (written-in data after correction)” into the memory. Step S21:the flow rate of the EGR valve that has completed writing the data intothe memory is inspected. Step S22: the flow rate measured by the flowrate inspection is added to the flow rates which have been measured sofar, to calculate the average flow rate. Then, the “sensor outputcorresponding to the valve opening degree” into which the flow rateerror of the EGR valve is incorporated is obtained by the methoddescribed in the first half process of the above first embodiment. Thiscompletes the first half process used for writing the data into thememory for the subsequent EGR valve.

In this manner, the number of samples for the flow rate to be measuredcan be increased each time the EGR valve is produced. Accordingly, theaccuracy of correspondence between the “operation flow rate” and the“actual flow rate” can be improved each time the EGR valve is produced.In addition, although this second embodiment measures the flow rate ofthe EGR valve that has completed writing the data into the memory, theflow rate measurement for product inspection of the produced EGR valveis utilized. Consequently, the increase in number of productionprocesses is restricted. Thus, the method for making the EGR valve inthis second embodiment can improve the precision of correspondencebetween the “operation flow rate” and the “actual flow rate” with thenumber of production processes limited.

Third Embodiment

A third embodiment will be described below. With respect to more thanone EGR valve used in the “first half process” of the above firstembodiment (more than one initial EGR valve for which the flow rate ismeasured to obtain “written-in data after correction”), “uncorrecteddata (see Step S1)” is written into their memories. After that, theabove-described Step S11 is not performed.

Accordingly, this third embodiment performs the above Step S11 also onmore than one EGR valve used in the “first half process” of the firstembodiment to write the “written-in data after correction” into thememory of the opening degree sensor 9. Thus, this third embodimentoverwrites the “written-in data after correction” into the memory of theEGR valve (memory of the EGR valve used in Steps S1 to S5) into whichthe “uncorrected written-in data” is written.

As described above, in this third embodiment, by overwriting the“written-in data after correction” into the memories of more than oneEGR valve used in the “first half process” of the first embodiment,highly accurate correspondence can be made between the “operation flowrate” and the “actual flow rate” even for “more than one initial EGRvalve”.

Industrial applicability of the present disclosure will be describedbelow. In the above embodiments, the examples of application of thepresent disclosure to the EGR valve have been illustrated, but thedisclosure is not limited to the examples. Thus, the present disclosuremay be applied to various valve devices that make flow rate adjustmentby the open-control.

The above embodiments illustrate that an angle sensor is used as aspecific example of the opening degree sensor, but the presentdisclosure is not limited to this example. As a specific example, thepresent disclosure may be applied to a valve device including a slidesensor if the valve 3 is slide-operated. Thus, the sensor output of theslide sensor may be corrected using the present disclosure.

Characteristics of the method for making the valve device of the aboveembodiments can be described as follows.

According to the method for making the valve device of the presentdisclosure, the flow rate error is obtained using more than onepreviously-produced valve device, and the “sensor output correspondingto the valve opening degree (referred to as written-in data aftercorrection)” into which this flow rate error is incorporated is obtained(first half process). The “written-in data after correction” obtained inthis first half process is written into a memory of anothersubsequently-produced valve device (valve device whose flow rate is notmeasured) (second half process). Accordingly, the number of processescan be limited. Moreover, according to the method for making the valvedevice of the present disclosure, the “written-in data after correction”is obtained using the average flow rate of more than one valve device.As a result, influence of a differential pressure variation causedduring each individual flow rate measurement can be restrained. Thus, adefect such as variation in “written-in data after correction” due tothe influence of the differential pressure variation caused during flowrate measurement can be avoided, and highly accurate correspondence canthereby be made between the “operation flow rate” and the “actual flowrate”. In this manner, the method for making the valve device of thepresent disclosure can suppress increase in number of processes and makecorrespondence between the “operation flow rate obtained from the sensoroutput” and the “actual flow rate through the valve device”.

While the present disclosure has been described with reference toembodiments thereof, it is to be understood that the disclosure is notlimited to the embodiments and constructions. The present disclosure isintended to cover various modification and equivalent arrangements. Inaddition, while the various combinations and configurations, othercombinations and configurations, including more, less or only a singleelement, are also within the spirit and scope of the present disclosure.

What is claimed is:
 1. A method for making a valve device including: apassage through which fluid passes; a valve that makes opening degreeadjustment of the passage; and an opening degree sensor that produces asensor output corresponding to a valve opening degree of the valve andthat includes a memory into which the sensor output corresponding to thevalve opening degree is written, the method comprising: performing afirst process, wherein: the valve device is one of a predeterminednumber of valve devices; and the performing of the first processincludes: measuring flow rates of the predetermined number of valvedevices; calculating a flow rate error based on an average flow rateobtained by averaging the measured flow rates; and obtaining the sensoroutput corresponding to the valve opening degree into which the flowrate error is incorporated; and performing a second process after thefirst process has been performed, wherein the performing of the secondprocess includes writing the sensor output corresponding to the valveopening degree obtained in the first process into the memory of anothersubsequently-produced valve device whose flow rate is not measured; andwherein the predetermined number is more than one.
 2. The methodaccording to claim 1, further comprising: measuring a flow rate of thevalve device that has completed writing the sensor output into thememory in the second process; and reflecting the measured flow rate inthe sensor output corresponding to the valve opening degree used forwriting the sensor output into the memory of the subsequently-producedvalve device.
 3. The method according to claim 1, wherein the firstprocess includes: an average flow rate calculation process, whereby flowrate measurement is performed with the predetermined number of valvedevices, with the sensor output corresponding to the valve openingdegree written into memories of the predetermined number of valvedevices, to calculate the average flow rate; and a matching process,whereby the average flow rate, the sensor output from the opening degreesensor, and the valve opening degree of the valve are matched together.4. The method according to claim 1, wherein the performing of the firstprocess includes performing the flow rate measurement at a plurality ofvalve opening degrees.
 5. The method according to claim 4, wherein theperforming of the first process includes performing the flow ratemeasurement at least when the valve opening degree is fully closed andfully open.
 6. The method according to claim 1, wherein the valve deviceis an exhaust gas recirculation (EGR) valve that adjusts an openingdegree of an EGR passage for returning a part of exhaust gas dischargedfrom an engine to an intake passage of the engine as EGR gas.